An inflatable vehicle occupant restraint, such as an air bag, is inflated to protect an occupant of a vehicle upon the occurrence of a vehicle collision. The air bag is part of a vehicle occupant restraint system which further includes a collision sensor and an inflator. The collision sensor senses vehicle conditions which indicate the occurrence of a collision. When the collision sensor senses a collision-indicating condition of at least a predetermined threshold level, the inflator is actuated. The inflator then emits inflation fluid which inflates the air bag into the vehicle occupant compartment to help protect an occupant of the vehicle from forcefully striking parts of the vehicle as a result of the collision.
The manner in which the air bag affects movement of the vehicle occupant can be influenced by factors such as the force with which the occupant moves against the air bag and the pressure of the inflation fluid in the air bag. Those factors, in turn, can be influenced by the severity of the collision and the ambient temperature of the inflator.